Field of the Invention
The present invention relates to a key guide structure for a keyboard instrument, which is applied to a keyboard instrument, such as an electronic piano, and configured to guide a key pivotally moved by key depression.
Description of the Related Art
Conventionally, the present applicant has already proposed a key guide structure for a keyboard instrument e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 2015-81930. In this key guide structure, a key having a rear end thereof pivotally supported is formed with a guide recess opening downward, and below the guide recess, there is erected a key guide holder having a key guide body mounted on an upper end thereof. The key guide body is made of elastomer and is formed in a plate shape having a lateral width substantially equal to a distance between left and right guide walls of the guide recess. The key guide body has a lubricant, such as grease, applied to left and right side surfaces thereof.
In the above-described key guide structure, when a key is in a key-released state, an upper end of the associated key guide body is engaged with the inside of the guide recess of the key in a state slightly inserted therein. In this state, when the key is depressed, the key guide body is deeply inserted into the guide recess while being held in sliding contact with the left and right guide walls of the guide recess, to thereby guide the key being pivotally moved while preventing the key from swinging in the left-right direction, i.e. while preventing lateral swing of the key.
However, since the key guide body is formed to have a lateral width substantially equal to the distance between the left and right guide walls of the guide recess of the key, friction between the key guide body and the left and right guide walls of the guide recess can be increased due to variation in manufacturing or mounting of the key guide body, and further depending on environment (temperature and humidity) in which the associated keyboard instrument is used. In this case, when the key is depressed, the touch weight of the key can be made larger than necessary or returning motion of the depressed key can be made slow. By securing a clearance between the left and right side surfaces of the key guide body and the respective left and right guide walls of the guide recess, it is possible to solve the above-mentioned problem caused by increased friction, but depending on the size of the clearance, it is sometimes impossible to sufficiently prevent the lateral swing of the key. Further, in this case, when a lateral force acts on the key during key depression to bring the guide wall of the guide recess into contact with the key guide body, there is a possibility that noise is generated or even a possibility that the key is brought into contact with a key adjacent thereto. Thus, the conventional key guide structure leaves room for improvement.